Official standards/Grades of powders | Indian Pharmacopoeia

During the process of size reduction, it is not possible to obtain the particle of uniform size.  Hence special technique is used to separate particles of a specified size, which is known as the process of size separation. Size separation is also known as sieving, sifting, screening. This technique is based on physical differences b/w the particles such as size, shape and density

When the fineness of the powder is described by means of a number, it is intended that all the particles of the powder shall pass through a sieve of which the nominal mesh aperture, in µm , is equal to that number.

Official Standard for Powder: IP (Indian Pharmacopoeia)

Coarse or fineness of powder is expressed by Reference  to the nominal mesh aperture size of the sieve through which powder is able to pass.

  • Indian pharmacopoeia- 5 grade of powder
S. No.Grade of powderall particles must pass through Sieve No. /Nominal mesh apertureSieve through which 40% of the particles pass/ Nominal mesh aperture
1Coarse powder 10 /(1700 µm)44 /(355 µm)
2Moderately coarse powder22 /(710 µm)60/ (250 µm)
3Moderately fine powder44/(355 µm)85/(180 µm)
4Fine powder85/(180 µm)Not specified
5Very fine powder120/(125 µm)Not specified
Grade of power: Size Separation
S. No.Grade of powder Comparison of powder size
1Coarse powder 1
2Moderately coarse powder1/6
3Moderately fine powder1/24
4Fine powder1/90
5Very fine powder1/2000
Comparison of Powder size by Grade of Powder

Note: 1.70 mm=1700 µm

Garde of powder as per Indian Pharmacopoeia/IP

A) Coarse Powder:

  • All the particles of which pass through a sieve with nominal mesh aperture of 1.70 mm/1700 µm (Sieve No. 10 ) and not more than 40% pass through nominal mesh aperture of 355 µm (Sieve No. 44) is called a Coarse Powder.

B) Moderately Coarse Powder: 

  • All the particles of which pass through a sieve with nominal mesh aperture of 710 µm (Sieve No. 22) and not more than 40% pass through nominal mesh aperture of 250 µm (Sieve No. 60) is called a Moderately Coarse Powder.

C) Moderately Fine Powder:

  • All the particles of which pass through a sieve with nominal mesh aperture of 355 µm (Sieve No. 44) and not more than 40% pass through nominal mesh aperture of 180 µm (Sieve No. 85) is called a Moderately Fine Powder.

D) Fine Powder: 

  • All the particles of which pass through a sieve with nominal mesh aperture of 180 µm (Sieve No. 85) is called a Fine Powder.

E) Very Fine Powder:

  • All the particles of which pass through a sieve with nominal mesh aperture of 125 µm (Sieve No. 120) is called a Fine Powder.
  • Note:
    • For Fine & Very fine grade of powder: IP has prescribed only the upper limit (Fine & Very fine)
    • Fineness of powder is described by means of Number: it indicates that all particles of powder shall pass through that sieve number (respective nominal mesh aperture in µm).

f) Microfine powder

A powder of which not less than 90 percent by weight of the particles pass through a sieve with a nominal mesh aperture of45 µm.

G) Superfine powder

A powder of which not less than 90 percent by a number of the particles are less than 10 µm in size.

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